1. The Field of the Invention
The present invention relates generally to systems and methods for delivering electronic messages. More particularly, embodiments of the invention related to evaluating behavioral information about senders of incoming messages and determining whether to allow incoming messages from approved senders to be delivered directly to a recipient's inbox.
2. The Relevant Technology
Electronic messaging or e-mail has become, for many people, a primary means of communication. The ease by which a person is able to send and receive an electronic message makes this form of communication extremely attractive. Unfortunately, others utilize electronic messaging to send unsolicited bulk electronic messages, better known as “spam.” Unsolicited electronic messages may include commercial advertisements, political messaging, as well as pornographic solicitations. Due to the influx of unsolicited electronic messages, people have become wary of giving out their electronic addresses for fear that their address will be sold to would-be solicitors. Further, those who receive spam are often not able to successfully request removal from mass e-mailing lists. Moreover, it is difficult to ascertain who has sent unsolicited electronic messages, since solicitors often use fabricated addresses or refrain from including one altogether.
Challenge and response mechanisms have been developed as a way to filter out unwanted electronic messages. When an electronic message is directed to a recipient, the message is delivered to the recipient only if the sender is identified as being authorized to send electronic messages to the recipient. Usually, the recipient has a list of approved senders, allowing the electronic message from the approved senders to be sent to the recipient's inbox without a challenge.
However, when the sender is unknown, a challenge message is sent to the sender to verify that the sender's address is valid and that the sender is a person as opposed to a machine before delivering the sender's email to the recipient's inbox. The sender is confirmed by asking the sender to respond to the challenge message in a way that affirmatively verifies that the sender is a person as opposed to a machine. This challenge/response method is quite successful in eliminating unsolicited electronic messages that are sent by mass-mailers.
However, challenge/response systems are based on a set of rules that do not take into consideration certain scenarios situations in which it is likely that a sender is sending a legitimate email message and it is likely that a recipient would actually like to receive an incoming message from the sender. In these situations, the challenge/response system is overinclusive, meaning that the spam protection actually prevents wanted messages from being sent directly to the recipient.